Janus Electrocatalytic Membrane Enables Tunable Redox via Sequential Tactics toward Ultrafast Water Decontamination

Emerging contaminants (ECs) in water are a prominent environmental concern worldwide. Despite advanced oxidation or reduction being appealing transformation approaches, existing technologies face challenges in adaptability to the removal of both electron-rich ECs and ECs with electron-withdrawing moieties. Here, a Janus electrocatalytic membrane was fabricated to induce hydroxyl radicals (^•OH) and atomic hydrogen (H*) simultaneously and tune redox processes via sequential tactics to achieve adaptable and ultrafast removal of diverse ECs. The Janus electrocatalytic carbon-fiber membrane with single-atom (SA) Fe and Ni anchored on two different sides, respectively, exhibited an excellent performance in the degradation of various ECs and treatment of the secondary effluent of pharmaceutical wastewater. Model ECs like propranolol and chloramphenicol were 100% removed at a high water flux (680 L m^-2 h^-1) and low energy consumption (<0.015 kWh m^-3 log^-1). In the electrofiltration sequence of Side-Fe to -Ni, the ^•OH yield was enhanced due to the flow-enhanced mass transfer of Side-Fe-induced H₂O₂ to Side-Ni-induced H* and the subsequent reaction to form ^•OH, favoring electron-rich organic degradation. While in the opposite sequence, the process of H*-mediated reduction followed by ^•OH-mediated oxidation achieved thermodynamical superiority, favoring the degradation of ECs with electron-withdrawing groups. This study highlighted a new reversible membrane design enabling tunable redox for the removal of various ECs from wastewater.